The present invention relates to a digital signal recording/reproducing apparatus for recording digital signals on a recording medium and/or reproducing the signals from the medium, or in particular to a digital signal recording apparatus having the function of protecting the copyright of the digital signal recorded in a recording medium.
The recent progress of the research on the compression of video and audio data using the digital technique has facilitated the storage and transmission of the data. This has greatly promoted the digitization of the broadcasting techniques.
A system is known, for example, in which analog video and audio signals are encoded by digital compression with high efficiency using the MPEG (moving picture experts group) standard and broadcast through a satellite or a coaxial cable. An apparatus for receiving the digital broadcasting is a digital broadcast receiver called the set top box.
A technique for receiving the digital signal transmitted with a plurality of information multiplexed to select the desired program is described in JP-A-8-56350.
As a home-use apparatus for recording and reproducing video and audio signals, on the other hand, an optical disc recorder is under development, which is capable of recording and reproducing the digital video and audio signal compressed and encoded digitally for the digital TV broadcasting, etc.
The digital broadcast receiver and the optical disc recorder are connected to each other by a digital interface, and are capable of storing the received digital broadcast with a high quality. The digital signal transmitted through a digital interface, if fee-charging or the need arises otherwise, requires protection to prevent illegal duplication.
A method for protecting the digital signal transmitted through the digital interface is described, for example, in xe2x80x9c5C Digital Transmission Content Protection White Paper, Revision 1.0, Jul. 14, 1998xe2x80x9d.
When the optical disc recorder described above has the function of encoding an analog signal input thereto into a digital signal of the same format as for the digital broadcasting and recording it in a recording medium, the recording operation is required to be compatible with the recording medium for recording data using the digital signal protection technique described above.
An object of the present invention is to provide a digital signal recording/reproducing apparatus which solves the problem mentioned above and can protect the copyright of the digital signal on the recording medium for the analog input information encoded into a digital signal.
Another object of the invention is to provide a digital signal recording/reproducing apparatus in which the external analog information encrypted and recorded in a DVD medium for copyright protection are decoded and reproduced from the same DVD medium.
According to an aspect of the invention, there is provided a digital signal recording apparatus comprising: an encoder circuit which encodes an input analog signal into a digital signal; a key information generating circuit which generates at least one key information; a key generating circuit which generates a key by executing a predetermined calculation on the key information input thereto; an encryption circuit which is supplied with the key and the digital information, and encrypts and outputs the digital signal using the same key; and a recording circuit which records at least the key information described above and recording it in a predetermined area of the recording medium together with the encrypted digital signal.
Other objects, features and advantages of the present invention will become apparent from the following detailed description of the embodiments of the invention taken in conjunction with the accompanying drawings.